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SONOGRAPHY CANADA CORE (PHYSICS)-
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SONOGRAPHY CANADA CORE (PHYSICS)-
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SONOGRAPHY CANADA CORE (PHYSICS)What is a transducer? - answers-anything that converts one form of energy to another
form of energy
What does an ultrasound transducer do? - answers-converts electropotential energy
into mechanical and mechanical energy into electropotential energy
What is the curie point? - answers-if a crystal is heated beyond the curie point (360
degrees for pzt) the crystal can lose piezoelectric effects
What material is traditionally used for ultrasound trasnducers? - answers-lead ziconate
titanate (pzt)
What are modern transducers made out of? - answers-composite materials to achieve
greater conversion efficiency with less of an acoustic impedance mismatch
Near zone (fresnel) - answers-the area between the face of the transducer and the
beam focus
Far zone (fraunhofer) - answers-region past the focus
Focus - answers-where the beam reaches its minimum diameter
Focal region - answers-region over whch the beam is most tightly focused
Detail resolution - answers-ability to distinguish between two objects in any of the three
dimensions (axial,lateral, elevational)
Operating frequency - answers-center frequency of the transmit bandwidth
What are four methods of focusing the ultrasound beam - answers-1)lenses
2)curved elements
3)electronic focusing
4)mirrors
Define lateral resolution. What are other names for lateral resolution? - answers-the
ability to resolve two structures as well as the limit to measurement accuracy in the
lateral dimension of an image
Side by side, angular, transverse, azimuthal
Lateral resolution is equal to.... - answers-lateral bandwidth
, Define elevation resolution. What are other names - answers-ability to resolve two
structures as well as the limit to measurement accuracy in the elevation dimension
What are the four acoustic variables? - answers-pressure
Density
Temperature
Particle motion
If a wave needs a medium to propagate it is a(n) __________ wave? - answers-
mechanical
What is the wavelength equation - answers-wavelength=propagation velocity/frequency
What is amplitude? - answers-measure of the strength or size of a physical quantity.
Voltage is a measure of electrical amplitude
Constructive interference (in phase waves) - answers-adding two signals that are in
phase
Occurs when two waves interact to produce a larger single wave
Destructive interference (out of phase waves) - answers-when two waves are aligned
such that the peak of one wave aligns with the minimum of the other wave, the waves
have a phase difference of 180 and are completely out of phase
Cancel each other other.
Partial constructive (partially destructive) - answers-waves are out of phase with each
other but not perfectly out of phase (less than 180 degrees). Produces an affect that is
between constructive and destructive
Frequency and period are - answers-reciprocals
What is frequency - answers-measure of how often an event occurs per time
Unit: cycles per second (hertz)
What is the period? - answers-represents the time that transpires between the
occurrence of one compression and the occurrence of the next compression
What is the propagation velocity? - answers-refers to how fast a wave travels within a
medium and is determined by the properties of the medium
With a higher density - answers-the bulk modulus increases (incompressible, inelastic,
stiff) and increases the propagation velocity
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